Chambers 1991

Methods	Purpose: to compare reminders for all, half or none of their participants to internal medicine residents to give influenza vaccination Design: RCT, resident physicians randomised Duration of study: 2 months Interval between intervention and when outcome was measured: 1 October to 30 November 1987 Power computation: not performed Statistics: Chi2, multiple logistic regression
Participants	Country: USA Setting: Family Practice Center of Thomas Jefferson University, Philadelphia Eligible participants: (health status); all participants ≥ 65 Age: ≥ 65 Gender 74% f
Interventions	Intervention 1: reminders to internal medicine residents for all participants to give influenza vaccination Intervention 2: reminders to half of participants Control: no reminders
Outcomes	Outcome measured: % influenza vaccination Time points from the study that are considered in the review or measured or reported in the study: 1 October to 30 November 1987 % vaccinated by: 30 November 1987
Notes	Funding: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"All physicians in the practice were stratified based on level of training and randomly assigned to one of three groups via a computerised randomization program"
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding (performance bias and detection bias) All outcomes	Low risk	No statement, but influenza vaccinations recorded by computerised billing system
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	2493 eligibles, of whom 864 visited clinic during 2‐month study period, of these 168 excluded (had already received influenza vaccine or saw several physicians), 24 made drop‐in visits, leaving 686 for randomisation, of whom 464 ≥ 65; average 10% had received influenza vaccination previous year
Selective reporting (reporting bias)	Low risk	No selective reporting